Perineuronal glial system in the cerebral ganglion of active and hibernating Helix aspersa

The electron microscopical changes in the glial lacunar network that surrounds the large neurons of meso- and metacerebrum of land snail cerebral ganglia were considered, in order to get an insight into the functional role of this peculiar structure in invertebrates. Compared with snails during the active period, in the hibernating animals the extension of glial processes was reduced and the glial processes appeared more regular and stacked around neurons. Moreover, they did not form deep, long interdigitations with neuronal infoldings as during the active period. In particular, data on the ultracytochemical detection of alkaline phosphatase and Ca²⁺/Mg²⁺-ATPase enzyme activities, point to a correlation between the extension of the glial system and its function in the regulation of the extracellular environment. In fact, in hibernating snails, lower reactivity was found on the glial membranes, including those of the trophospongium.